Inhibition of nitrergic relaxations by a selective inhibitor of the soluble guanylate cyclase

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Abstract
. The actions of 1H‐[1,2,4]oxadiazolo[4,3,‐a]quinoxalin‐1‐one (ODQ), a specific inhibitor of the soluble guanylate cyclase (SGC), were investigated in the rabbit anococcygeus muscle. . ODQ (1 nM‐1 μm) inhibited in a concentration‐dependent manner the relaxations induced by electrical field stimulation (EFS; 50 V, 0.3 ms duration, 1 Hz, for 5 s, every 120 s). . ODQ (1 μm) also inhibited the relaxations elicited by EFS (50 V, 0.3 ms duration, 1, 2.5, 5, 10 Hz, for 5 s) and sodium nitroprusside (SNP; 1 μm) without affecting those induced by isoprenaline (1 μm), atrial natriuretic peptide (ANP; 100 nM) or an analogue of cyclic GMP (8‐pCPT‐cyclic GMP; 500 μm). . ODQ (1 μm) inhibited the elevations in the concentration of cyclic GMP induced by SNP or EFS, but not by ANP. ODQ did not affect the concentrations of cyclic AMP. . Nitrergic relaxation in this tissue appears, therefore, to be mediated via activation of SGC.